It has been found that the prior art cutter knife falls into two categories, i.e. the fixed type and the telescopic type. However, it is necessary to dismantle the handle of the fixed type cutter knife in order to replace the blade thereby making it inconvenient to use. Further, regarding the telescopic type cutter knife, the blade thereof will be forced into the handle when a relatively large force is applied thereto.
Therefore, it is an object of the present invention to provide an improved knife which may obviate and mitigate the above-mentioned drawbacks.